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Re: Static? Dynamic?

From: Dan Connolly <connolly@w3.org>
Date: Tue, 29 Jun 1999 17:50:16 -0500
Message-ID: <37794DA8.B57C22B1@w3.org>
To: roconnor@uwaterloo.ca
CC: www-talk@w3.org
Russell Steven Shawn O'Connor wrote:
> 
> On Tue, 29 Jun 1999, Dan Connolly wrote:
> 
> > Russell Steven Shawn O'Connor wrote:
> > > HTML was designed to serve up more or less static pages.
> >
> > Huh? Please cite a source.
> 
> Maybe I'm misunderstanding what people mean by static and dynamic.
> 
> By static I mean the information at a URI is relatively constant.  One
> shouldn't expect the contents of the URI to become out dated in the time
> it takes to read the page.  As Grahame Grieve just put it, "why should a
> user perceive any difference between a page they got from going back and a
> page they got from going forward?"  I'd say the answer it that they
> shouldn't.

I prefer that my browser's back button shows me what I've
seen before, rather than the current state of the resource.
(this brings up the whole issue of consistency, trust, etc.,
which I'll save for another day...)

But I can see where this could be confusing...

>  If the information on the page is changing that fast, then
> there should be an applet there (or something) that itself keeps the page
> up to date.
> 
> >From one point of view, looking up a query inot a telephone database is
> dynamic.  The page doesn't really exist anywhere, and is created on the
> fly.  But it another respect it seems static, virtualy static as it were.
> The same URI for the query will more or less always return the same
> result.

Aha... yes, now I see what you're saying... and yes, the
design of the web does assume (or at least optimize for)
slowly-changing state.
(I started writing about this at http://www.w3.org/Architecture/state
but never really got anywhere...)

But it's perfectly reasonable to publish a resource that
is "the current score of the NBA playoff game" that would
change quite rapidly, provided you label it with the
relevant metadata (expires, time-to-live, whatever).
If I visited such a resource, then followed a link, then
came back, I'd prefer to see the *old* score, plus
a "dead fish" or whatever that tells me I'm looking at
stale info.

The problem is: so few pages declare their TTL that caches
have to assumes something like 24hours, and so providers
of dynamic services have to commit all sorts of hackery
to work around those caches. Sigh.


>  A user can't tell that the page is dynamicaly created because it
> acts exactly the same way any other page acts.  So from a users stand
> point one would consider these pages static.
> 
> ... Am I making any sense here?

yes. Thanks for clarifying.

-- 
Dan Connolly, W3C
http://www.w3.org/People/Connolly/
Received on Tuesday, 29 June 1999 18:50:23 GMT

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